Statistical physics of complex networks..pdf

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1、STATISTICALPHYSICSOFCOMPLEXNETWORKSByHUAFENGXIEAdissertationsubmittedtotheGraduateFacultyinPhysicsinpartialfulfill-mentoftherequirementsforthedegreeofDoctorofPhilosophy,TheCityUniversityofNewYork2008331318633131862008©2008HUAFENGXIEAllRightsReservediiThismanuscripthasb

2、eenreadandacceptedfortheGraduateFacultyinPhysicsinsatisfactionofthedissertationrequirementforthedegreeofDoctorofPhilosophy.BrianSchwartzDateChairofExaminingCommitteeSultanCattoDateExecutiveOfficerSergeiMaslovJosephKriegerStevenASchwarzSupervisoryCommitteeTHECITYUNIVERS

3、ITYOFNEWYORKiiiAbstractSTATISTICALPHYSICSOFCOMPLEXNETWORKSByHUAFENGXIEAdviser:ProfessorBrianSchwartzWeliveinaconnectedworld.Itisofgreatpracticalimportanceandintellec-tualappealtounderstandthenetworkssurroundingus.Inthisworkwestudyrankingofthenodesincomplexnetworks.Inla

4、rgenetworkssuchasWorldWideWeb(WWW)andcitationnetworksofscientificliterature,searchingbykeywordsisacommonpracticetoretrieveusefulinformation.OntheWWW,apartfromthecontentsofwebpages,thetopologyofthenetworkitselfcanbearichsourceofinformationabouttheirrelativeimportanceand

5、relevancytothesearchquery.Itistheeffectiveutilizationofthistopologicalinformation[50]whichadvancedtheGooglesearchenginetoitspresentpositionofthemostpopulartoolontheWWW.TheWorld-WideWeb(WWW)ischaracterizedbyastrongcommunitystructureinwhichcommunitiesofwebpagesaredensely

6、interconnectedbyhyperlinks.WestudyhowsuchnetworkarchitectureaffectstheaverageGooglerankingofindividualwebpagesinthecommunity.Usingamean-fieldapproximation,wequantifyhowtheaverageGooglerankofcom-munity’swebpagesdependsonthedegreetowhichitisisolatedfromtherestivoftheworl

7、dinbothincomingandoutgoingdirections,andα–theonlyintrin-sicparameterofGoogle’sPageRankalgorithm.Weproceedwithnumericalstudyofsimulatednetworksandempiricalstudyofseveralinternalweb-com-munitieswithintwoUSuniversities.Thepredictionsofourmean-fieldtreat-mentwerequalitativ

8、elyverifiedinthosereal-lifenetworks.Furthermore,thevalueα=0.15usedbyGoogleseemstobeoptimizedforthedegreeofisola-tiono